This invention relates to an antiperspirant stick which includes a macroporous highly cross-linked polymer. More particularly, the invention includes a stick product that contains small porous polymer particles which are free of any "in situ" entrapped active ingredient.
The concept of producing spheres and beads of a macroporous polymer is old in the art, as well as the use of such macroporous structures for the entrapment and subsequent delivery of certain active ingredients. One example of this concept may be found in U.S. Pat. No. 4,690,825, issued Sep. 1, 1987, in which a suspension polymerization process is employed to produce beads from a monomer system including styrene and divinylbenzene. Mineral oil is entrapped "in situ" and the beads are said to possess utility in various cosmetic applications. In U.S. Pat. No. 4,719,040, issued Jan. 12, 1988, a macroporous polymer laden with perfume is incorporated into an air freshener gel. U.S. Pat. No. 4,724,240, issued Feb. 9, 1988, European Patent No. 61,701, granted Jul. 16, 1986, and Canadian Patent No. 1,168,157, issued May 29, 1984, each relate to "in situ" entrapped emollients and moisturizers carried within macroporous beads. Various cosmetic and toiletry applications of these products are disclosed.
A macroporous polymer entrapping an emollient is taught in U.S. Pat. No. 4,764,362, issued Aug. 16, 1988, and in U.S. Pat. No. 4,813,976, issued Mar. 21, 1989, in which the polymer is incorporated into a nail conditioning emery board. During filing of the nails, the emollient is released in order to condition and lubricate the nails. A similar concept is taught in U.S. Pat. No. 4,776,358, issued Oct. 11, 1988, in which a dental floss includes flavor oils entrapped in certain "microsponges". Suspension polymerized macroporous polymer beads are taught in U.S. Pat. No. 4,806,360, issued Feb. 21, 1989, and in U.S. Pat. No. 4,855,144, issued Aug. 8, 1989, wherein melanin pigment is incorporated into the macroporous structure and applied to the skin and said to function as a sunscreen. Similar bead structures are also taught in European Patent Application Publication No. 306 236A2, published Mar. 3, 1989, and in Patent Cooperation Treaty International Publication No. WO 88/01164, published Feb. 25, 1988.
A reticulated polyurethane foam is disclosed in U.S. Pat. No. 4,828,542, issued May 9, 1989, having macroporous polymer particles bonded to the foam. The particles entrap a liquid soap and the foam functions as a cleaning pad. In U.S. Pat. No. 4,855,127, issued Aug. 8, 1989, and U.S. Pat. No. 4,880,617, issued Nov. 14, 1989, hydrophobic polymeric porous beads are used as a free-flowing solid carrier for various pheromones, pesticides, fragrances, and chemicals entrapped therein. Hydrophilic beads are formed in U.S. Pat. No. 4,870,145, issued Sep. 26, 1989, and upon removal of the solvent used to form the voids, the beads possess various utilities including incorporation into contact lens cleaners, facial scrubs, and tile cleaners. In U.S. Pat. No. 4,873,091, issued Oct. 10, 1989, resilient microbeads are formed by suspension polymerizing curable elastomers such as isoprene rubbers to produce porous rubber beads. The porous rubber beads are employed in topical applications. In the Patent Cooperation Treaty International Publication No. W089/10132, published Nov. 2, 1989, porous particles are disclosed as an ingredient in personal care emulsions. A pet litter is described in U.S. Pat. No. 4,881,490, issued Nov. 21, 1989, and U.S. Pat. No. 4,883,021, issued Nov. 28, 1989, wherein a macromolecular polymer entrapping a fragrance is incorporated in an animal litter to slowly release fragrance for combating odors.
In U.S. Pat. No. 4,898,913, issued Feb. 6, 1990, macroporous hydrophobic powder materials are rendered hydrophilic by treatment of the surface of the powder. In one embodiment of the '913 patent, the surface is saponified whereas in another embodiment an acrylate monomer is polymerized on the surface. A wet wipe useful in personal care applications is disclosed in U.S. Pat. No. 4,904,524, issued Feb. 27, 1990, wherein macroporous polymeric beads containing a silicone skin conditioner are incorporated into the surface of a paper sheet. Polymeric microparticles loaded with a fungicide are taught in U.S. Pat. No. 4,923,894, issued May 8, 1990. In U.S. Pat. No. 4,933,372, issued Jun. 12, 1990, there is described rigid resin particles formed by polymerizing monounsaturated and polyunsaturated monomers within the pores of inorganic template particles such as silica gel, silica, alumina, zirconia, and metal oxides. The template particles are dissolved leaving porous adsorptive particles which mirror the template particles in size, surface area, and porosity.
In accordance with the present invention however, an antiperspirant stick product is formed containing macroporous polymer particles which are free of any "in situ" entrapped active ingredient in contrast to the particles of the prior art. The empty macroporous particles function as a bulking agent in the stick product and reduce the amount of settling during processing of the stick product. The particles enable stick products to be formulated with less amounts of the waxy material ingredient, and therefore the empty macroporous polymer particles enhance the antiperspirant effectiveness of the stick product since the particles do not interfere with the mobility of the astringent compounds as do the waxy material ingredient of such formulations.